This invention relates to a device for acting at a point on an information carrying medium, for instance for punching holes or printing characters, composed of dots, dashes or the like, in a medium such as a tape or sheet. In this type of device, a point or the like for acting on the medium is adapted to be struck or pressed against a surface of the medium. An elongated arm extends primarily parallel to the surface, is provided with or has the form of said point at one of its ends, and is connected to a spring device in the region of its other end. In addition, the arm is under the influence of a drive device and is resiliently swingable in a direction to or from the surface of the medium.
Such arms can be used as printing arms in printing heads of matrix type, i.e. in which the printed characters are formed of a number of dots. In printing heads of this kind, the printing arms must reciprocate at a very high frequency to obtain a more rapid printing speed. As a result, problems limiting the printing speed often occur. Even if the printing point fastened on the arm can be made to strike the recording medium with a short delay and at a high speed, difficulties in the return movement of the arms often occur. Evidently, this movement must also be very rapid in order not to limit the printing speed. On the other hand, the return movement must be stopped in such a way that the arms attain their rest position without a tendency to bounce. To this end, some kind of a mechanical damper is often used, for instance a rubber cushion, for absorbing the kinetic energy. However, in practice this solution functions badly, e.g., due to wear, which rapidly destroys the damper.
Similar problems also occur in tape punchers.